Air compressor

ABSTRACT

Disclosed is an air compressor including a cylinder including a recessed compression chamber, and an orbiter including a frame forming a main body and a piston rod protruding from the frame, wherein the piston rod includes a piston rod inner circumferential surface and a piston rod outer circumferential surface, the piston rod having an ending part formed at its end to protrude from the frame, a diameter of an imaginary circle derived from the curvature formed on the ending part formed at the end of the piston rod is larger than a width ranging from the piston rod inner circumferential surface to the piston rod outer circumferential surface, the piston rod is shaped of a transformed ring having a non-continuous portion, the piston rod inner circumferential surface is an inner circumferential surface shaped of the transformed ring, the piston rod outer circumferential surface is an outer circumferential surface shaped of the transformed ring, and the ending part is defined by the non-continuous portion of the transformed ring. Therefore, in compressing the external air due to a contact between the closed surface of the terminal portion of the compression chamber and the ending part of the terminal portion of the piston rod, a contact area is increased, thereby increasing the compressive force of the air compressor.

TECHNICAL FIELD

The present invention relates to an air compressor, and more particularly, to an air compressor having an increased compressive force.

BACKGROUND ART

In general, a rotary air compressor is a device that seals a given volume of a chamber with gas and reduces the volume closed with gas using a piston or a rotor to increase the pressure of air. In particular, the rotary air compressor is widely used in a wide variety of industrial fields, such as a compressor for vehicle maintenance or machine fabrication, a compressor used in construction sites, air tools, and so on, owing to various advantages including achievement of compactness and lightness in weight, reduction in vibrations and noises, and so on.

As a representative example of the rotary air compressor, a small compressor is disclosed by other applicants in Korean Patent Registration No. 10-0323063. The disclosed small compressor is configured such that a rotation shaft, which rotates by a motor disposed at a lower end of a casing, is inserted into a shaft hole of a first housing, a circular space having a ring gear provided in its inner circumferential surface is integrally formed inside of a movable body rotating with the ending part of the rotation shaft, a ring gear formed at the inner circumferential surface of the rotating member contacting the circular space is provided in a second housing coupled to the first housing, linear gears of a rotation suppressing device are engaged with the ring gears so that cam motion is performed in the movable body and the circular space of the second housing, and a circular vane, which is connected to a circular compression chamber of the second housing and inserted into the ring-shaped operating hole, is integrally formed to receive air through an air supply hole. The rotation shaft is capable of rotating with stability while being subjected to a centrifugal force by a weight of its one side, ring-shaped operating holes are symmetrically formed at both sides of the movable body and air is compressed by a a circular vane inserted into the ring-shaped operating holes, the air compressed in a compressed space formed by the ring-shaped operating holes is moved to the compressed space after receiving the compressed air through a moving hole of the movable body, thereby discharging the air to a discharge hole formed in the right side of a concave portion of the circular vane and moving the compressed air to an air storage chamber to then be collected within the casing through the discharge hole of the compressed air.

However, since the rotary air compressor operates such that when the movable body and the ring-shaped operating holes rotate based on left-right symmetrical configuration, they continuously strike the circular vane and the inner wall of the second housing, as disclosed in the prior art registered patent (Korean Patent Registration No. 10-0323063), considerably high operating noises are generated. In addition, since the circular vane and the second housing are integrally formed, a molding working becomes complicated, thereby significantly increasing the fabrication time and cost.

Among various types of rotary air compressors proposed for addressing the above problems, the applicant of the present invention filed an application entitled “Air compressor” on Feb. 29, 2009 (Korean Patent Application No: 10-2009-0013659). The air compressor is configured such that when an orbiter is engaged with a compression chamber as an air compressed space, the compression chamber is defined into two chambers, that is, first and second compression chambers, and the orbiter alternately reduces volumes of the first and second compression chambers while performing an eccentric rotating motion with stability in the compression chamber in linkage with a holder ring, thereby providing compressed air.

That is to say, compared to the conventional rotary air compressors, the above-described “air compressor” has a simplified coupling structure in which while an eccentric rotation shaft having rotational power applied from an external power source rotates, when an orbiter compressively installed on the eccentric rotation shaft performs an eccentric motion along a compression chamber, a holder ring coaxially installed on the eccentric rotation shaft and the orbiter triggers a stable eccentric cam motion in the compression chamber. Therefore, the proposed air compressor can effectively compress the air, thereby noticeably lowering the manufacturing cost.

In the above-described air compressor, however, the holder ring for inducing a stable cam motion is coupled only to the center of the orbiter, making it quite difficult for the orbiter to trigger the stable cam motion when the orbiter having a predetermined amount of eccentricity performs an eccentric rotary motion.

Accordingly, the applicant of the present invention filed an application entitled “Rotary air compressor” on Apr. 15, 2010 (Korean Patent Application No: 10-2010-0034840). The rotary air compressor is capable of attenuating vibrations due to an eccentric rotary motion by installing three driven holders equidistantly while coaxially rotating with an eccentric rotation shaft on a circumferential surface of an orbiter constituting the air compressor disclosed in Korean Patent Application No. 10-2009-0013659.

Here, both of the air compressor disclosed in Korean Patent Application No. 10-2009-0013659 and the rotary air compressor disclosed in Korean Patent Application No. 10-2010-0034840 are configured such that a piston rod of an orbiter selectively reduces volumes of first and second compression chambers of the compression chamber while performing an eccentric rotary motion in a compression chamber of a cylinder, thereby discharging the compressed air to an air outlet.

Accordingly, when the piston rod performs an eccentric motion in the compression chamber, sealing capacity between the piston rod and the compression chamber is an important factor in view of compressive force of the air compressor. Therefore, in order to increase the compressive force of the air compressor, it is necessary to increase the sealing capacity between the piston rod and the compression chamber.

DISCLOSURE OF THE INVENTION

In order to overcome the above-mentioned shortcomings, the present invention provides an air compressor having an increased compressive force by increasing sealing capacity of a piston rod and a compression chamber.

The above and other objects of the present invention will be described in or be apparent from the following description of the preferred embodiments.

According to an aspect of the invention, there is provided an air compressor including a cylinder including a recessed compression chamber, and an orbiter including a frame forming a main body and a piston rod protruding from the frame, wherein the piston rod includes a piston rod inner circumferential surface and a piston rod outer circumferential surface, the piston rod having an ending part formed at its end to protrude from the frame, a diameter of an imaginary circle derived from the curvature formed on the ending part formed at the end of the piston rod is larger than a width ranging from the piston rod inner circumferential surface to the piston rod outer circumferential surface, the piston rod is shaped of a transformed ring having a non-continuous portion, the piston rod inner circumferential surface is an inner circumferential surface shaped of the transformed ring, the piston rod outer circumferential surface is an outer circumferential surface shaped of the transformed ring, and the ending part is defined by the non-continuous portion of the transformed ring.

The ending part may include a first end and a second end, and the first end and the second end may be defined by the non-continuous portion without the piston rod protruding therefrom.

In addition, the compression chamber may include a compression chamber inner circumferential surface and a compression chamber outer circumferential surface, the compression chamber including a closed surface at an end to be recessed inside the cylinder, and a diameter of an imaginary circle derived from the curvature formed on the closed surface at the end of the compression chamber may be larger than a width ranging from the compression chamber inner circumferential surface to the compression chamber outer circumferential surface.

In addition, the closed surface may include a first closed surface and a second closed surface, and the first closed surface and the second closed surface may be defined by the closed part in which the compression chamber is not recessed.

The cylinder may further include an air intake foamed to penetrate one side of the compression chamber with respect to the closed part and an air outlet formed to penetrate the other side of the compression chamber.

ADVANTAGEOUS EFFECTS

As described above, according to the present invention, in compressing the external air due to a contact between the closed surface of the terminal portion of the compression chamber and the ending part of the terminal portion of the piston rod, a contact area is increased, thereby increasing the compressive force of the air compressor.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects, features and advantages of the present invention will be more apparent from the following detailed description in conjunction with the accompanying drawings, in which:

FIGS. 1 to 3 are schematic diagrams illustrating a compressed state of a general rotary air compressor;

FIG. 4 is a schematic diagram illustrating a compression chamber of the general rotary air compressor;

FIG. 5 is a schematic diagram illustrating a piston rod of the general rotary air compressor shown;

FIG. 6 is a diagram illustrating that the general rotary air compressor is not perfectly closed;

FIG. 7 is a plan view illustrating a cylinder of an air compressor according to the present invention;

FIG. 8 is a cross-sectional view of the cylinder of the air compressor according to the present invention;

FIG. 9 is a bottom view of the cylinder of the air compressor according to the present invention;

FIG. 10 is a schematic diagram illustrating a compression chamber of the cylinder of the air compressor according to the present invention;

FIG. 11 is a plan view illustrating an orbiter of the cylinder of an air compressor according to the present invention;

FIG. 12 is a cross-sectional view of the orbiter of the cylinder of the air compressor according to the present invention;

FIG. 13 is a bottom view of the orbiter of the cylinder of the air compressor according to the present invention; and

FIGS. 14 to 22 are schematic diagrams illustrating a compressed state of an air compressor according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Advantages and features of the present invention and methods of accomplishing the same may be understood more readily by reference to the following detailed description of preferred embodiments and the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the concept of the invention to those skilled in the art, and the present invention will only be defined by the appended claims. In the drawings, the size and relative sizes of layers and regions may be exaggerated for clarity.

Reference will now be made in detail to the present embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These teems are only used to distinguish one element from another element. Thus, for example, a first element, a first component or a first section discussed below could be termed a second element, a second component or a second section without departing from the teachings of the present invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Spatially relative terms, such as “beneath”, “below”, “lower”, “above”, “upper”, and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures.

Example embodiments will now be described more fully hereinafter with reference to the accompanying drawings.

FIGS. 1 to 3 are schematic diagrams illustrating a compressed state of a general rotary air compressor. The general rotary air compressor may correspond to the air compressor disclosed in Korean Patent Application No. 10-2009-0013659 or the rotary air compressor disclosed in Korean Patent Application No. 10-2010-0034840.

First, referring to FIG. 1, in the general rotary air compressor, a piston rod 320 constituting an orbiter (not shown) is installed in each of the compression chambers 251 and 252 constituting a cylinder 200. The piston rod 320 defines the compression chamber into two chambers, that is, the first compression chamber 251 and the second compression chamber 252 while performing an eccentric motion in the compression chamber.

Here, the orbiter (not shown) performs an eccentric rotary motion in linkage with the eccentric rotary motion of an eccentric rotation shaft (not shown), as disclosed in Korean Patent Application No. 10-2010-0034840, and the air supplied through an air intake 220 is compressed by selectively shrinking the first compression chamber 251 or the second compression chamber 252.

In addition, the compressed air is selectively discharged to a first air outlet 230 or a second air outlet 240.

In more detail, referring to FIG. 2, if the eccentric rotation shaft (not shown) is rotated by applying power as a driving power source in the course of absorbing the air into the first and second compression chambers 251 and 252 through the air intake 220, the orbiter (not shown) performs an eccentric rotary motion along inner circumferential surfaces of the first and second compression chambers 251 and 252. During this process, in a state in which the air absorbed into the first compression chamber 251 is compressed by shrinking the first compression chamber 251, the piston rod 320 constituting the orbiter (not shown) discharges the compressed air to the first air outlet 230 and then closes the first air outlet 230.

Next, referring to FIG. 3, if the eccentric rotation shaft (not shown) continues to rotate using the power from the driving power source, the orbiter (not shown) performs an eccentric rotary motion along outer circumferential surfaces of the first and second compression chambers 251 and 252. During this process, in a state in which the air absorbed into the second compression chamber 252 is compressed by shrinking the second compression chamber 252, the piston rod 320 constituting the orbiter (not shown) discharges the compressed air to the second air outlet 240 and then closes the second air outlet 240.

In the general rotary air compressor in which the piston rod performs an eccentric rotary motion along the inner circumferential surface of the compression chamber, perfect sealing is not achieved at each terminal portion of the piston rod and the compression chamber, that is, at a contact portion between the ending part of the piston rod and the closed surface of the compression chamber, and gaps (G1 and G2 of FIGS. 2 and 3) may be created, which will later be described.

FIG. 4 is a schematic diagram illustrating a compression chamber of the general rotary air compressor, FIG. 5 is a schematic diagram illustrating a piston rod of the general rotary air compressor and FIG. 6 is a diagram illustrating that the general rotary air compressor is not perfectly closed.

Referring first to FIG. 4, in the general rotary air compressor, a compression chamber 253 of a cylinder is recessed by a width W1 ranging from a compression chamber inner circumferential surface to a compression chamber outer circumferential surface.

In addition, when an imaginary circle with a diameter d1 is formed derived from the curvature formed on the closed surface at the terminal portion of the compression chamber 253, the compression chamber 253 of the cylinder is recessed by the diameter d1.

Here, the width W1 ranging from the compression chamber inner circumferential surface to the compression chamber outer circumferential surface and the diameter d1 of the imaginary circle formed derived from the curvature formed on the closed surface at the terminal portion of the compression chamber 253 may be equal to each other.

Next, referring to FIG. 5, in the general rotary air compressor, the piston rod 320 of the orbiter protrudes by a width W2 ranging from a piston rod inner circumferential surface to a piston rod outer circumferential surface.

In addition, when an imaginary circle with a diameter d2 is formed derived from the curvature formed on the ending part at the terminal portion of the piston rod 320 of the orbiter, the piston rod 320 of the orbiter protrudes by the diameter d2.

Here, the width W2 ranging from the piston rod inner circumferential surface to the piston rod outer circumferential surface and the diameter d2 of the imaginary circle derived from the curvature formed on the ending part at the terminal portion of the piston rod 320 may be equal to each other.

That is to say, as shown in FIGS. 4 and 5, the recessed compression chamber has an equal width or diameter as a whole, and the protruding piston rod 320 has an equal width or diameter as a whole.

Accordingly, as shown in FIGS. 1 to 3, when the piston rod performs is an eccentric rotary motion along the inner circumferential surface of the compression chamber, sealing capacity may be lowered at each terminal portion of the piston rod and the compression chamber, that is, at the contact portion between the ending part of the piston rod and the closed surface of the compression chamber, due to a limited contact area, thereby lowering the compressive force of the air compressor.

That is to say, as shown in FIG. 6, for example, in a case where two perfect circles 252 and 320 make contact with each other, they contact each other at a point P. However, since the general air compressor has a non-perfectly circular portion, for example, a closed part 260, the gaps G1 and G2 shown in FIGS. 2 and 3 may be created.

Accordingly, taking the importance of increasing the sealing capacity between the piston rod and the compression chamber into consideration, the applicant of the present invention proposes structures of a piston rod and a compression chamber for increasing the sealing capacity.

Meanwhile, as will later be described, the air compressor of the present invention features a compression chamber of a cylinder and a piston rod of an orbiter. The other functional elements, except for the compression chamber and the piston rod, including, for example, a cylinder-frame coupling structure, a cylinder-orbiter coupling structure, a configuration of an eccentric rotation shaft and a coupling structure thereof, and a configuration of a driven holder and a coupling structure thereof, are substantially the same as those of the air compressor disclosed in Korean Patent Application No. 10-2009-0013659 and the rotary air compressor disclosed in Korean Patent Application No. 10-2010-0034840, and detailed descriptions thereof will be omitted.

In addition, since the air compressor according to the present invention features the compression chamber of the cylinder and the piston rod of the orbiter, the functional elements other than the compression chamber and the piston rod may be freely changed without restriction in view of kind and type.

FIG. 7 is a plan view illustrating a cylinder of an air compressor according to the present invention, FIG. 8 is a cross-sectional view of the cylinder of the air compressor according to the present invention, FIG. 9 is a bottom view of the cylinder of the air compressor according to the present invention, and FIG. 10 is a schematic diagram illustrating a compression chamber of the cylinder of the air compressor according to the present invention.

First, referring to FIGS. 7 to 9, in the air compressor according to the present invention, a cylinder 600 includes a compression chamber 653 recessed into the cylinder. That is to say, the compression chamber 653, which is shaped of a circular ring, is recessed into the cylinder, and has one side sealed with a closed part 650, an air intake 620 is formed to penetrate one side of the compression chamber 653 with respect to the closed part 650, and a first air outlet 630 and a second air outlet 640 are formed to penetrate the other side of the compression chamber 653 with respect to the closed part 650.

That is to say, the compression chamber is shaped of a circular ring, which corresponds to a non-continuous circular ring, in which the compression chamber is not recessed in the closed part 650. Hereinafter, the shape of the compression chamber will be defined as a transformed ring shape including a non-continuous portion.

In more detail, the compression chamber 653 includes a compression chamber inner circumferential surface 655 and a compression chamber outer circumferential surface 656 and has a first closed surface 661 and a second closed surface 662 at its terminal portion to then be recessed into the cylinder. Here, the first closed surface 661 and the second closed surface 662 are defined by the closed part 650.

Meanwhile, as shown in FIG. 8, in the air compressor according to the present invention, the cylinder 600 may further include an eccentric space recessed at its central area in addition to a compression chamber, which is, however, not a characteristic part of the present invention, and a detailed description thereof will be omitted. As to this feature, the rotary air compressor disclosed in Korean Patent Application No. 10-2010-0034840 may be referred to.

Next, referring to FIG. 10, in the air compressor according to the present invention, the compression chamber 653 of the cylinder is recessed by a width W3 ranging from a compression chamber inner circumferential surface to a compression chamber outer circumferential surface.

In addition, when an imaginary circle with a diameter d3 is derived from the curvature formed on a closed surface at a terminal portion of the compression chamber 653, the compression chamber 653 of the cylinder is recessed by the diameter d3.

In the present invention, the diameter d3 of the imaginary circle derived from the curvature formed on the closed surface at the terminal portion of the compression chamber 653 is larger than the width W3 ranging from the compression chamber inner circumferential surface to the compression chamber outer circumferential surface.

That is to say, the diameter d3 of the imaginary circle derived from the curvature formed on the closed surface at the terminal portion of the compression chamber 653 is made to be larger than the width W3 ranging from the compression chamber inner circumferential surface of a portion of the compression chamber other than the terminal portion to the compression chamber outer circumferential surface, thereby increasing a contact area between the compression chamber and a cylinder rod of an orbiter, which will later be described.

FIG. 11 is a plan view illustrating an orbiter of the cylinder of an air compressor according to the present invention, FIG. 12 is a cross-sectional view of the orbiter of the cylinder of the air compressor according to the present invention, and FIG. 13 is a bottom view of the orbiter of the cylinder of the air compressor according to the present invention.

Referring to FIGS. 11 to 13, in the air compressor according to the present invention, the orbiter 700 includes a frame 730 forming a main body and a piston rod 720 protruding to a rear surface of the frame 730.

The frame 730 is a part receiving rotational power from an eccentric rotation shaft (not shown) and performing an eccentric motion and the piston rod is accommodated in the compression chamber 653 constituting the cylinder 600 shown in FIGS. 7 to 10. According to the eccentric motion of the frame 730, external air induced through the air intake 620 is compressed in the compression chamber 653 to then be discharged to the first air outlet 630 and the second air outlet 640.

In more detail, the piston rod 720 of the orbiter 700 accommodated in the compression chamber 653 shaped of a transformed ring does not perform an eccentric rotary motion by the closed part 650 constituting the cylinder 600 but performs an eccentric cam motion along the inner and outer circumferential surfaces of the compression chamber 653.

The piston rod 720 of the orbiter 700 will now be described in detail. The piston rod 720 includes a piston rod inner circumferential surface 765 and a piston rod outer circumferential surface 755, and has a first end 761 and a second end 762 at its terminal portion to protrude from a frame. Here, the first end 761 and the second end 762 are defined by a non-continuous portion 750 without the piston rod protruding therefrom.

That is to say, the piston rod 720 is shaped of a circular ring, which corresponds to a non-continuous circular ring, in which the piston rod 720 does not protrude in the non-continuous portion 750. Hereinafter, the shape of the piston rod 720 will be defined as a transformed ring shape including a non-continuous portion. The shape of the piston rod 720 is substantially the same as or similar to the shape of the compression chamber.

Meanwhile, as shown in FIG. 11, in the air compressor according to the present invention, the orbiter 700 may further include an eccentric groove recessed at its central area and a concave groove recessed at its periphery, which are, however, not characteristic parts of the present invention, and detailed descriptions thereof will be omitted. As to these features, the rotary air compressor disclosed in Korean Patent Application No. 10-2010-0034840 may be referred to.

Next, referring to FIG. 13, in the air compressor according to the present invention, the piston rod 720 of the orbiter 700 protrudes by a width W4 ranging from an inner circumferential surface 756 of the piston rod 720 to an outer circumferential surface 755 of the piston rod 720.

In addition, when an imaginary circle with a diameter d4 is derived from the curvatures formed on the first end 761 and the second end 762 at the terminal portion of the piston rod 720, the orbiter 700 protrudes by the diameter d4.

In the present invention, the diameter d4 of the imaginary circle derived from the curvature formed on an ending part at the terminal portion of the piston rod 720 is larger than the width W4 ranging from the piston rod inner circumferential surface to the piston rod outer circumferential surface.

That is to say, the diameter d4 derived from the curvatures formed on the first end 761 and the second end 762 at the terminal portion of the piston rod 720 is made to be larger than the width W4 ranging from the piston rod inner circumferential surface of a portion of the compression chamber other than the terminal portion to the piston rod outer circumferential surface, thereby increasing a contact area between the piston rod and the compression chamber of the cylinder.

FIGS. 14 to 22 are schematic diagrams illustrating a compressed state of an air compressor according to the present invention.

Referring to FIGS. 14 to 22, in the air compressor according to the present invention, the piston rod 720 constituting an orbiter (not shown) is installed in the compression chambers 651 and 652 constituting the cylinder. The piston rod 720 defines the compression chamber into two compression chambers, that is, the first compression chamber 651 and the second compression chamber 652 while performing an eccentric motion in the compression chamber.

Here, the orbiter (not shown) performs is an eccentric rotating motion in linkage with an eccentric rotating motion of the eccentric rotation shaft (not shown), as disclosed in Korean Patent Application No: 10-2010-0034840, and the air supplied through the air intake 620 is compressed by selectively shrinking the first compression chamber 651 or the second compression chamber 652.

In addition, the compressed air is selectively discharged to a first air outlet 630 or a second air outlet 640.

In more detail, if the eccentric rotation shaft (not shown) is rotated by applying power as a driving power source in the course of absorbing the air into the first and second compression chambers 651 and 652 through the air intake 620, the orbiter (not shown) performs an eccentric rotary motion along the inner and outer circumferential surfaces of the first and second compression chambers 651 and 652. During this process, in a state in which the air absorbed into the first compression chamber 651 is compressed by shrinking the first compression chamber 651, the piston rod 720 constituting the orbiter (not shown) discharges the compressed air to the first air outlet 630 and then closes the first air outlet 630.

Next, if the eccentric rotation shaft (not shown) continues to rotate using the power from the driving power source, the orbiter (not shown) performs an eccentric rotary motion along the outer circumferential surfaces of the first and second compression chambers 651 and 652. During this process, in a state in which the air absorbed into the second compression chamber 652 is compressed by shrinking the second compression chamber 652, the piston rod 720 constituting the orbiter (not shown) discharges the compressed air to the second air outlet 640 and then closes the second air outlet 640.

Here, undefined reference numeral 660 denotes a central shaft of the cylinder and undefined reference numeral 730 denotes a central shaft of the orbiter.

Meanwhile, as described above, in the present invention, the diameter of the imaginary circle derived from the curvature formed on the closed surface formed at the terminal portion of the compression chamber is larger than the width ranging from the compression chamber inner circumferential surface to the compression chamber outer circumferential surface.

In addition, in the present invention, the diameter of the imaginary circle derived from the curvature formed on the ending part formed at the terminal portion of the piston rod is larger than the width ranging from the piston rod inner circumferential surface to the piston rod outer circumferential surface.

Accordingly, in the present invention, in compressing the external air due to a contact between the closed surface of the terminal portion of the compression chamber and the ending part of the terminal portion of the piston rod, the contact area may be increased.

That is to say, as shown in FIGS. 4 and 5, in the general air compressor, the recessed compression chamber has an equal width or diameter as a whole, and the protruding piston rod has an equal width or diameter as a whole. Accordingly, when the piston rod performs an eccentric rotary motion along the inner circumferential surface of the compression chamber, sealing capacity may be lowered at each terminal portion of the piston rod and the compression chamber, that is, at the contact portion between the ending part of the piston rod and the closed surface of the compression chamber, due to a limited contact area, thereby lowering the compressive force of the air compressor.

As described above, according to the present invention, in compressing the external air due to a contact between the closed surface of the terminal portion of the compression chamber and the ending part of the terminal portion of the piston rod, the contact area may be increased, thereby increasing the compressive force of the air compressor.

Although exemplary embodiments of the present invention have been described in detail hereinabove, it should be understood that many variations and modifications of the basic inventive concept herein described, which may appear to those skilled in the art, will still fall within the spirit and scope of the exemplary embodiments of the present invention as defined by the appended claims.

As described above, according to the present invention, since compactness and lightness in weight can be achieved by increasing a compressive force of the air compressor and vibrations and noises can be reduced, the air compressor can be widely used in a variety of industrial fields, including vehicle maintenance, machine fabrication, construction sites, air tools, and so on,

<Explanation of Reference Numerals> 600: Cylinder 620: Air intake 630, 640: Air outlet 653: Compression chamber 655: Compression chamber inner circumferential surface 656: Compression chamber outer circumferential surface 661, 662: Closed surface 650: Closed part 700: Orbiter 730: Frame 720: Piston rod 761, 762: Ending part 755: Piston rod outer circumferential surface 756: Piston rod inner circumferential surface 

What is claimed is:
 1. An air compressor comprising: a cylinder including a recessed compression chamber; and an orbiter including a frame forming a main body and a piston rod protruding from the frame, wherein the piston rod includes a piston rod inner circumferential surface and a piston rod outer circumferential surface, the piston rod having an ending part formed at its end to protrude from the frame, a diameter of an imaginary circle derived from the curvature formed on the ending part formed at the end of the piston rod is larger than a width ranging from the piston rod inner circumferential surface to the piston rod outer circumferential surface, the piston rod is shaped of a transformed ring having a non-continuous portion, the piston rod inner circumferential surface is an inner circumferential surface shaped of the transformed ring, the piston rod outer circumferential surface is an outer circumferential surface shaped of the transformed ring, and the ending part is defined by the non-continuous portion of the transformed ring.
 2. The air compressor of claim 1, wherein the ending part includes a first end and a second end, and the first end and the second end are defined by the non-continuous portion without the piston rod protruding therefrom.
 3. The air compressor of claim 1, wherein the compression chamber includes a compression chamber inner circumferential surface and a compression chamber outer circumferential surface, the compression chamber including a closed surface at an end to be recessed inside the cylinder, and a diameter of an imaginary circle derived from the curvature formed on the closed surface at the end of the compression chamber is larger than a width ranging from the compression chamber inner circumferential surface to the compression chamber outer circumferential surface.
 4. The air compressor of claim 3, wherein the closed surface includes a first closed surface and a second closed surface, and the first closed surface and the second closed surface are defined by the closed part in which the compression chamber is not recessed.
 5. The air compressor of claim 4, wherein the cylinder further includes an air intake formed to penetrate one side of the compression chamber with respect to the closed part and an air outlet formed to penetrate the other side of the compression chamber. 